The clamped members such as bolt, nut, and the like, have been so far widely used for fastening together various kinds of building articles or railroad ties and rails. For instance, referring to the railroad ties and rails, as indicated in FIG. 14, a press spring 103 having a plate-like portion 102 laid over between a tie 100 and a rail 101 is pressed down by clamping a bolt n to the tie 100 to fix the rail 101 on the tie 100. However, if the rail 101 is subjected to vibration repeatedly, the bolt n may loosen automatically even though the bolt n undergoes the biasing force of the press spring 103.
On the other hand, for instance, referring to the wooden buildings, columns and beams are fixed directly to each other using building strap bolts, but even if a nut is completely clamped down, or a nut having a function of stopping rotation is used, there may still yield a gap between the nut, column, and beam when the lumbers used dry off to such a degree that the column and beam shrinks and the nut can no longer press down on the column and achieve its clamping function. Such being the case, the inventor of the present invention has invented an automatic clamping device for strap bolt in order to solve this task. As can be seen in FIG. 15, this specific device comprises a cylindrical rotator a, a tubular casing b for receiving the rotator a in a manner that the latter is rotatable and slidable axial and vertical, and a coiled spring c wound around the rotator a to give the turning effort to the rotator a, wherein the rotator a has an engaging portion a1 on the inner periphery thereof for receiving a nut n which is threadedly engaged with a strap bolt, and a projection a2 extending in an outward direction of the diameter on the outer periphery of the upper end. Also on the lower end of the casing b a drive-fit/fixing means b1 such as a nail, and on the inner periphery a depression b2 for receiving the projection a2 in a manner that the latter is kept unrotatable. With the nut n fitted in the engaging portion a of the rotator a, and affixing the casing b by the drive-fit/fixing means b1 in the column or beam as a mount element with the nut attached thereto, the rotator a slides toward the upper end of the casing b, then, the projection a2 goes out of the depression b2, and the rotator a biased by the coiled spring c gives a turning effort to the nut n fitted in the engagement portion so that the nut n can always be held in an energized position. With the nut n being kept operative at all times, if the lumber becomes dry and the gap between the nut n and the column becomes wider, the nut n will automatically turn under the influence of the coiled spring c, whereby the close contact between the nut n and columun h1 can be maintained.
Although the casing b can be fixed by driving into the wood, the drive-fit/fixing means b1, such as nail provided on the upper end of the casing b, the metallic press spring 103 affixed in the railroad rail 101 as shown in FIG. 14 is kept pressed down by the bolt n, the casing b can not be fixed to the tie by the driven fixing means bl such as a nail because the metallic press spring 103 is disposed around the bolt n. Consequently, it would be difficult to adapt the automatic clamping device for building strap bolt as illustrated by FIG. 15 to bolt or nut fitted in the metallic mount element 101, 103.
In view of the circumstances, as described above the first object of the present invention provide an automatic screw clamping device which is capable of preventing a bolt fitted in the metallic mount element from loosening by retightening the bolt.
A second object of this invention is to provide an automatic screw clamping device which can be readily and for a short time fitted to the metallic mount element. A third object of the present invention is to provide an automatic screw clamping device for fixing a bolt to a railroad rail, which may be easily fitted to the fixing bolt for railroad rail. The fixing bolt is secured to the railroad rail in order to prevent the fixing bolt from loosening by automatically retightening the bolt.
A fourth object of the present invention is to provide an automatic screw clamping device which, while in use with nut or bolt, may be easily identified and detected even if it has been removed from the nut or bolt by other person with the intention of loosening the latter.